Twenty patients suffering from panic disorder with agoraphobia were administered the hostility subscale of Kellner's Symptom Questionnaire and the irritability scales of Paykel's Clinical Interview for Depression and of Kellner's Anxiety Rating Scale before and after behavioral treatment of agoraphobia. A matched control group of normal subjects had the same assessments at two similar points in time. Hostility and irritable mood decreased and friendliness increased in patients with panic disorder after treatment; upon recovery, there were no significant differences in hostility between patients and controls, whereas such differences were striking during the illness. The results suggest that increased hostility and irritable mood may be symptoms of panic disorder and improve with the treatment of agoraphobia.